Thermoplastic resin composition and its use

ABSTRACT

A thermoplastic resin composition comprising 50 to 85 parts by weight of an ethylene-vinyl alcohol copolymer, 10 to 40 parts by weight of an ionomer of ethylene-unsaturated carboxylic acid copolymer containing about 5 to 12 mole % of unsaturated carboxylic acid, and 1 to 25 parts by weight of a polyamide and a packaging material comprising said resin composition are provided. The resin composition is excellent in gas barrier property, impact resistance, pinhole resistance, stretchability, drawability and transparency and is preferably used for packaging material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thermoplastic resin composition withexcellent properties such as gas-barrier property, impact resistance,pinhole resistance, stretchability, drawability, and transparency, andalso relates to the use of the composition.

2. Description of the Prior Art

Ethylene-vinyl alcohol copolymers with a high vinyl alcohol content arewidely used as packaging material for food owing to their superiortransparency, gas-barrier property, etc. The Above-mentioned copolymers,however, are rarely used as a mono-layer film since they haveinsufficient flexibility, processability, stretchability, etc. Forexample, when these copolymers are molded into film by an inflationprocess, they have such drawbacks that acceptable molding conditions toobtain satisfactory products from these copolymers are restricted in anarrow range and that longitudinal wrinkles are liable to be formedaround pinch rolls. There is another drawback that pinholes are apt tobe formed when a film is exposed to repeated deformation such asfolding. Such drawbacks can be overcome by blending ethylene polymers,etc., which have excellent flexibility and processability with saidcopolymer. In many cases, however, addition of ethylene polymers, etc.,loses transparency of ethylene-vinyl alcohol copolymers and has not yetbeen adopted widely.

For example, JP A 40-107351 (1974) discloses that addition of ionomer toethylene-vinyl alcohol copolymer can improve flexibility. Since thisproposal aims at improving adhesiveness of said copolymer topolyolefins, it teaches a technique to add substantial quantities ofpolyamide as well. This proposal neither considers transparency norrefers to composition of the ionomers.

JP A 50-103582 (1975) discloses an invention which also pays attentionto adhesiveness to polyolefins. It discloses laminate containerscomprising polyolefins and a composition similar to that in the previousproposal except that the quantity of polyamide blended is smaller. Itneither makes consideration on transparency nor discloses use ofionomers in detail although it mentions that zinc ionomer and sodiumionomer can be employed. It only shows examples of using Surlyn 1652specifically.

According to the investigation of the present inventors, it is revealedthat blending of ionomer with ethylene-vinyl alcohol copolymer improvesflexibility and processability but deteriorates transparencysignificantly, and that flexibility and processability are improved buttransparency is significantly damaged also in a system in which Surlyn1652 and polyamide is combined with ethylene-vinyl alcohol copolymer asshown in examples of JP A 50-103582 (1975).

The present inventors then have striven for investigation on compositionwhich overcomes the above-mentioned drawbacks of ethylene-vinyl alcoholcopolymer and does not damage transparency so much. As a result, it isrevealed that when ionomer of an ethylene-unsaturated carboxylic acidcopolymer having high content of unsaturated carboxylic acid componentand polyamide are blended at a predetermined ratio, flexibility,processability, impact resistance, tear strength, pinhole resistance,etc., can be improved without sacrificing transparency so much.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to improve drawbacksof ethylene-vinyl alcohol copolymer without damaging its transparency somuch.

The present invention relates to thermoplastic resin composition whichcomprises 50 to 85 parts by weight of an ethylene-vinyl alcoholcopolymer, 10 to 40 parts by weight of an ionomer ofethylene-unsaturated carboxylic acid copolymer containing 4 to 15 mol %of unsaturated carboxylic acid, and 1 to 25 parts by weight of apolyamide.

The present invention also relates to packaging material wherein thematerial has at least one layer of the thermoplastic resin compositionmentioned above.

The present invention is specifically characterized by that ionomer witha relatively high unsaturated carboxylic acid content, namelyethylene-unsaturated carboxylic acid copolymer containing 4 to 15 mol %of unsaturated carboxylic acid, is selected and blended, in combinationwith polyamide, with ethylene-vinyl alcohol copolymer.

That is, the combination of the above-mentioned components can improveflexibility, impact resistance, processability, etc. of ethylene-vinylalcohol copolymer, without decreasing transparency so much.

It is particularly important that ionomers used in the present inventioncontain unsaturated carboxylic acid in a range of 4 to 15 mol % in orderto maintain superior transparency and to improve impact resistance. Whena content of unsaturated carboxylic acid is lower than theabove-mentioned range, transparency and impact resistance tend todecrease (refer to Comparative Examples 1 and 2). When a content ofunsaturated carboxylic acid is excessively high, impact resistance alsotends to be reduced.

Polyamide is used in the present invention to make ethylene-vinylalcohol copolymer and ionomer compatible each other and therefore, thecombination of ionomer and polyamide can improve flexibility, impactresistance, processability, etc., without deteriorating opticalproperties including transparency.

When only ionomer is blended with ethylene-vinyl alcohol copolymer(refer to Comparative Example 6), transparency and impact resistancefall remarkably compared with that of ethylene-vinyl alcohol copolymeralone. When only polyamide is blended (refer to Comparative Example 7),impact resistance and processability are rarely improved. Their combinedaddition to ethylene-vinyl alcohol copolymer (refer to Embodiments 1 to9) can, however, achieve significant improvement of mechanicalproperties and processability without a noticeable reduction intransparency.

According to the present invention, it is important to use 50 to 85parts by weight of ethylene-vinyl alcohol copolymer, 10 to 40 parts byweight of ionomer, and 1 to 25 parts by weight of polyamide. When aquantity of ionomer used is below the above-mentioned range (refer toComparative Example 3), impact resistance and processability are notimproved sufficiently. On the other hand, when it exceeds theabove-mentioned range (refer to Comparative Example 4), gas-barrierproperties are reduced. When polyamide is used in a quantity smallerthan the above-mentioned range (refer to Comparative Examples 3 and 6),impact resistance is reduced, and when a quantity of polyamide is higherthan the above-mentioned range (refer to Comparative Example 5), thecomposition thus obtained has such drawbacks that its processability isseriously lowered and its heat-resistance is deteriorated.

Consequently, according to the present invention, addition of specificionomer and polyamide in predetermined quantities to ethylene-vinylalcohol copolymer can improve impact resistance, flexibility,processability, pinhole resistance, deep drawability, etc., withoutsacrificing excellent gas-barrier property, transparency, etc., of thecopolymer so much.

Furthermore, in the thermoplastic resin composition of the presentinvention, a polymer composition obtained by compounding 0.01 to 3 partsby weight of a metal salt of a fatty acid in 100 parts by weight of aresin component composed of 50 to 85 parts by weight of anethylene-vinyl alcohol copolymer, 10 to 40 parts by weight of an ionomerof ethylene-unsaturated carboxylic acid containing 4 to 15 mole % of anunsaturated carboxylic acid, and 1 to 25 parts by weight of a polyamidehas excellent heat stability. Accordingly, a marked advantage isobtained in that in melt molding, the formation of a gel is notrecognized, or the resin composition has a defect of coloration at amolding temperature of a relatively high temperature.

PREFERRED EMBODIMENTS OF THE INVENTION

Ethylene-vinyl alcohol copolymer of the present invention contains 40 to85 mol %, preferably 50 to 75 mol % of vinyl alcohol and may contain theother monomers by about 10 mol % or less. The best method to obtain suchcopolymers is to sponify ethylene-vinylacetate copolymer containing 40to 85 mol %, preferably 50 to 75 mol % of vinyl acetate until asaponification value of 95% or higher, preferably 98% or higher isobtained. Vinyl alcohol contents of the copolymer outside of theabove-mentioned range are not preferable: When it exceeds theabove-mentioned range, heat-resistance and processability become todeteriorate; whereas when it stays below the range, gas-barrier propertyis reduced. Preferably, ethylene-vinyl alcohol copolymer has a melt flowrate of 0.5 to 50 g/10 min, particularly 1 to 20 g/10 min at 210° C. andunder a load of 2.160 g.

Ethylene-unsaturated carboxylic acid copolymers to be converted intoionomers contain 4 to 15 mol %, preferably 5 to 12%, more preferably 6to 10 mol % of unsaturated carboxylic acid with the consideration ontransparency of composition. When the copolymer contains a unsaturatedcarboxylic acid content lower than the above-mentioned range, it isdifficult to obtain composition with superior transparency and impactresistance. Higher contents of unsaturated carboxylic acid of thecopolymer tend to improve transparency of composition, but may somewhatdecrease impact resistance. Therefore, it is preferable to usecopolymers with an acid content in the above-mentioned range. In thesecopolymers, not higher than 12 mol %, preferably not higher than 8 mol %of other monomers may be co-polymerized. These copolymers can beobtained by undergoing radical copolymerization with ethylene,unsaturated carboxylic acid or some other monomers required at a hightemperature and a high pressure.

Unsaturated carboxylic acids include, for example, acrylic acid,methacrylic acid, ethacrylic acid, maleic acid, monomethyl maleate,monoethyl maleate, and maleic anhydride. Acrylic acid and methacrylicacid are particularly prefered. Other monomers which may be contained inionomer include vinyl ester such as vinyl acetate and vinyl propionate,esters of unsaturated carboxylic acids such as methyl acrylate, ethylacrylate, 2-ethylhexyl acrylate, methyl methacrylate, isobutylmethacrylate, and diethyl maleate, and carbon monoxide.

Metal ions of ionomer are alkali metals including lithium, sodium andpotassium, alkaline earth metals such as calcium and magnesium, andzinc. Zinc is particularly preferred since it produces a good balance oftransparency and impact resistance. A neutralization degree of ionomersis in the range of 5 to 100%, preferably 10 to 90%, and more preferably30 to 70%.

It is preferred to use ionomers having a melt flow rate of 0.05 to 50g/10 min, particularly 0.5 to 5 g/10 min at 190° C. and under a load of2,160 g.

Nylon 6, Nylon 66, Nylon 610, Nylon 612, Nylon 11, Nylon 12, Nylon 6/66copolymer, Nylon 6/12 copolymer, Nylon 66/12 copolymer, Nylon 6/610copolymer. Nylon 66/610 copolymer, Nylon 6/6T, etc. can be mentioned aspolyamides used in the present invention. Polyamides listed above can beemployed whatever they are as far as they have enough molecular weightto be able to form film. Among these polyamides, those having a meltingpoint (DSC method) not higher than 240° C., particularly not higher than230° C. are preferred. Specifically, when melting point of polyamide istoo high, processing temperature is also required to be high, thus heatdeterioration of composition is very likely to increase. Copolyamide isadvantageously used to improve heat-resistance of composition because ofits low melting point.

In the present invention, ethylene-vinyl alcohol copolymer is present in50 to 85 parts by weight, more preferably 60 to 80 parts by weight,ionomer in 10 to 40 parts by weight, preferably 15 to 35 parts byweight, and polyamide in 1 to 25 parts by weight, preferably 3 to 15parts by weight when a total of ethylene-vinyl alcohol copolymer,ionomer, and polyamide is 100 parts by weight. A ratio of ionomer belowthe above-mentioned range provides a small degree of improvement inflexibility and pinhole resistance, whereas that beyond the rangeinduces unnegligible deterioration of gas-barrier property. Neither arepreferred. Although polyamide functions to make ethylene-vinyl alcoholcopolymer and ionomer compatible and to minimize reduction oftransparency, its content should not be higher than 25 parts by weightsince an excessive quantity of polyamide damages formability ofcomposition.

In the present invention, to further increase the heat stability of theresin composition, it is desirable to compound 0.01 to 3 parts byweight, especially preferably 0.03 to 2 parts by weight, of a metal saltof a fatty acid in 100 parts by weight of a resin component composed ofthe above ethylene-vinyl alcohol copolymer, the ionomer of theethylene-unsaturated carboxylic acid copolymer and the polyamide.

The thermal resin composition of this embodiment according to thisinvention in which a metal salt of a fatty acid is compounded caneffectively suppress the elevation of torque at the time of meltkneading.

This elevation of torque may be caused by the occurrence of crosslinkingof polymerizable components via thermal degradation (heat degradation orelimination of hydrogen or hydroxyl group) of polymeric components atthe time of melt kneading of the resin composition. It is presumed thata metal salt of a fatty acid used in the resin composition of thisembodiment of the present invention decreases the friction of polymerswith each other and simultaneously shows a heat-stabilizing action,whereby the elevation of torque is suppressed.

As examples of the metal salts of aliphatic fatty acids, it isexemplified metal salt of aliphatic fatty acid having about 12 to 24carbon atoms, especially about 16 to 20 carbon atoms, and include saltsof alkali metals, alkaline earth metals and zinc. More specifically,they include at least one sodium, potassium, calcium, magnesium and zincpalamitate, stearate, oleate, behanate, eruciate and hydroxy stearate.Calcium stearate is most preferably obtained at a low cost, and has ahigh addition effect.

Composition of the present invention may contain various kinds ofadditives as required. Such additives include anti-oxidants, thermalstabilizers, weather-proof stabilizers, anti-static agents, lubricants,and anti-blocking agents. Composition of the present invention may alsocontain other polymers as far as they do not damage properties of thecomposition.

Composition of the present invention can be easily obtained bymelt-blending components using an ordinary melt-blending apparatus. Inorder to obtain moldings of composition of the present invention,components are dry-blended or melt-blended, and molded directly. Whenkneading intensity is insufficient, however, physical properties such astransparency may deteriorate. Therefore, it is preferable to melt-blendcomposition to form pellets in advance, which are then used for variouskinds of molding since it provides moldings with stable properties.

Composition of the present invention can be used for various packagingmaterials owing to its properties mentioned above. These packagingmaterials can be molded into film (unoriented film, shrink film, etc.),sheet, cup, tray, bottle, tube, can paper carton and bag-in-box etc. bymolding methods such as extrusion molding, injection molding, blowmolding, thermoforming (with or without plug-assist), compressionmolding. Molding temperature varies depending on raw materials used.Preferred temperature, however, is in the range of 190 to 240° C.,preferably 200 to 230° C.

The above-mentioned moldings may be composed exclusively of compositionof the present invention or may be a laminate of 2 or more layers ofother various substrates. Other substrates which may be laminatedinclude, for example, polyolefins such as polyethylene, polypropylene,poly-1-butene, poly-4-methyl-1-pentene, ethylene copolymers such asethylene-vinyl acetate copolymer, ethylene-(metha)acrylic estercopolymer, ethylene-(metha)acrylic acid copolymer and its ionomer,ethylene-(metha)acrylic acid-(metha)acrylic ester copolymer and itsionomer, and ethylene-(metha)acrylic ester-maleic anhydride copolymer,polyamide, polyester, polyvinyl chloride, polyvinylidene chloride,polystyrene, paper, aluminum foil, and aluminum vapor deposition film.Among these substrates, laminate packaging materials having at least onelayer of olefinic polymer such as above mentioned polyolefins andethylene copolymers are advantageously used. Prior to laminating,olefinic polymer may wholly or partially undergo graft-modification withmonomer such as maleic anhydride, which may provide adhesiveness,alternatively, such graft-modified olefinic polymer may be used foradhesive layer and laminated with olefinic polymer which is notgraft-modified. Resin composition according to the present invention isadvantageously used for an intermediate layer and sandwiched between aninner and outer layer of low hydroscopic resin such as olefinic resin,because this laminated structure will deter a bad influence of anintermediate layer being moistened (deterioration of gas-barrierproperty by moisture).

More particularly, when composition of the present invention is denotedas C, the above-mentioned olefinic polymer as PO, modified olefinicpolymer as modified PO, polymide as PA, polyethylene terephthalate asPET, polystyrene as PS and polyvinyl chloride as PVC, possible laminatedstructure includes PO/C, PO/modified PO/C, PO/C/PO, PO/modifiedPO/C/modified PO/PO, PET/C/PET, PS/C/PS, PO/PA/C, PO/C/PA/PO,PO/paper/PO/C/PO.

EXAMPLES

The present invention will be further illustrated by the followingexamples which will not restrict the range of the present invention.

Firstly, a method of preparing resin composition of the presentinvention, a film processing method and methods of evaluating filmproperties will be illustrated below.

(1) Method of Preparing Resin Composition of the Present Invention

Resins with the compositions shown in Tables 1 and 2 were blendedaccording to the blending ratios shown in Table 3. Two blending methodswere adopted: Method A is that resin pellets in a solid state wereblended uniformly at room temperature using a blender, etc. (refer to asdry blend hereinafter). Method B is that resins were extruded whileheated and mixed using a single screw extruder to form pellets (refer toas melt blend hereinafter). Extruder conditions in the melt blend are asfollows:

Extruder aperture: 40 mm φ; resin temperature: 230° C.; resin extrusionrate: 10 kg/hr.

(2) Film Processing Method

Each composition blended by the methods mentioned in (1) above wasprocessed by a film machine using an extruder with an aperture of 30 mmor 50 mm. The blown film processing was conducted under the conditionsmentioned below:

Machine 1:

Extruder with an aperture of 30 mm, round dye with a diameter of 50 mm

Temperature of resin to be processed: 230° C.

Film thickness: 50 μm

Film blow-up ratio: 2.3

Line speed: 3 m/min

Machine 2:

Extruder with an aperture of 50 mm, round dye with a diameter of 150 mm

Temperature of resin to be processed: 230° C.

Film thickness: 50 μm

Film blow-up ratio: 2.4

Line speed: 6 m/min

(3) Methods of Evaluating Film Properties

The properties of films prepared according to the method described in(2) were determined according to respective methods and standards asfollows. All the following evaluations were done in 50% relativehumidity at 23° C., and the results are shown in Table 3.

    ______________________________________                                        Determination items                                                                           Determination method/Standard                                 ______________________________________                                        1)    Optical characters                                                            Haze          JIS K-6714                                                      Gloss         JIS Z-8741                                                      Transparency  ASTM D-1709                                               2)    Oxygen        JIS Z-1707                                                      permeability                                                            3)    Film impact   An inverted ball with a diameter                                              of 0.6 inch attached to a tip                                                 was knocked at the center of a                                                circular film stretched in a                                                  horizontal direction with a                                                   constant area and a strength at                                               which the film is ruptured is                                                 read. (Apparatus used: Film                                                   Impact Tester, Toyo Seiki Co.,                                                Ltd.)                                                     4)    Pinhole resistance                                                                          The number of pinholes is counted                                             when film is bent at a                                                        predetermined number of times                                                 under conditions of a twist angle                                             of 440° and a stroke of 152.4 m.                                       (Apparatus used: Gelnoflex                                                    Measurement Apparatus,                                                        Toyo Seiki Co., Ltd.)                                     5)    Vacuum Deep   Vacuum Deep Drawing Tester of                                   Drawing       Omori Kasei Co, Ltd. was used to                                Processability                                                                              evaluate melt stretching                                                      processability.                                                               Film heating duration: 2 seconds;                                             Vacuum drawing duration: 3                                                    seconds; Drawing dept: 60 mm;                                                 Film heating temperature: 140° C.                  6)    Modulus       JIS K6301                                                                     A film sample was punched by a                                                JIS No. 1 dumbbell and a stress                                               of longitudinal/transverse                                                    direction of film is measured                                                 when an elongation percentage is                                              2% at a tensile rate of 300                                                   mm/min. (Apparatus used:                                                      Universal Tester Shimadzu                                                     Corporation)                                              ______________________________________                                    

Example 1, Comparative Example 8

In Example 1, ionomers shown in Table 1 and 2, EVOH, and polyamide wereblended at a composition ratio of 21%:70%:9% by weight using the meltblend method mentioned in the resin composition preparation method in(1) to prepare composition, from which film was formed according to thefilm processing method in (2) (condition of Machine 1). Opticalcharacters (haze, gloss, and transparency), oxygen permeability, filmimpact, vacuum deep drawing processability, and modulus of the film weremeasured according to the method of evaluating film properties in (3).In Comparative Example 8, EVOH resin shown in Table was evaluated by thesame method. The results are shown in Table 3.

As a result, the resin composition film of Example 1 exhibited similaroptical characters and oxygen permeability as EVOH single film inComparative Example 8, and furthermore, showed significant improvementin film impact, vacuum deep drawing processability, and modula(flexibility).

Examples 2 and 4

Examples 2 and 4 were completely the same as Examples 1 and 3,respectively, except that the resin compositions were prepared by thedry blend method. Although film impact, oxygen permeability, vacuum deepdrawing processability, and modulus exhibited similar improvingtendencies of Example 1, optical characters were slightly worse thanthat prepared by the melt blend method.

Examples 3, and 5 and Comparative Examples 1, 2 and 10

Evaluation was conducted using the same method as in Example 1, exceptthat ionomers of composition were changed to those shown in Table 3. InExamples 3, and 5, respective items were improved at the level similarto that obtained in Example 1. Optical characters or film impact were,however, worse in Comparative Examples 1, 2, and 10.

Example 6

All the matters were the same as Example 1, except for alteration ofresin composition ratios.

Comparative Examples 3 to 5

Resin composition ratios were changed to those shown in Table 3 and thesame evaluation method as in Example 1 was conducted.

When quantities of ionomer and polyamide blended were too small to EVOH,melt stretchability and film impact were decreased as in ComparativeExample 3. On the other hand, when ratios of ionomer and polyamideincorporated were excessively high, film molding property was reduced orfilm became improcessable as shown in Comparative Example 5, and higherratios of ionomer and polyamide significantly increased oxygenpermeability and provided unfavorable results as shown in ComparativeExample 4.

Comparative Example 6

Polyamide was excluded from a resin composition and a two-componentcomposition consisting of EVOH and ionomer was prepared. As a result,optical characters and film impact were remarkably reduced, leading tounfavorable outcome.

Comparative Example 7

Ionomer was excluded from a composition and a two-component compositionconsisting of EVOH and polyamide was prepared. As a result, film impactwas reduced, vacuum deep drawing processability was lost, and modulusbecame higher than that of EVOH.

Example 7

Resin Composition identical to that of Example 1 was molded into filmusing a blown film machine with an extruder aperture of 50 mm accordingto the film processing method (Machine 2) described in (2). When anextruder became larger units scale, properties of the film remained atthe same levels as in Example 1. Thus, excellent blown filmprocessability and properties were observed.

Example 8

Resin composition identical to that in Example 2 was processed by thefilm processing method identical to that is Example 7. When an extruderbecame larger in its scale, properties of the film remained at the samelevels as in Example 2. Thus, excellent blown film processability andproperties were observed.

Comparative Example 9

For comparison, the EVOH resin shown in Table 2 was molded into film bythe film processing method identical to that in Example 7 and propertiesof the film were evaluated.

In Examples 7 and 8 and Comparative Example 9, pinhole resistance wasdetermined according to the method described in the methods ofevaluating film properties in (3). As a result, the number of bendinguntil pinholes appeared was significantly increased and an improvementof pinhole resistance was confirmed in Examples 8 and 9 as compared withComparative Example 9.

Example 9

Resin composition film was prepared using the same method as in Example1, except that 6-Ny in Example 1 was changed for 6, 12-Ny (UBE). Theemployment of 6, 12-Ny (UBE), which has a lower melting point than 6-Ny,allowed the resin temperature in melt blending and film processing to belowered from 230° C. to 210° C. without increasing the resin pressureand motor loading of extruder. This effectively serves to reduce heatdeterioration as well as cross-linking during a long-term operation ofmolding resin composition.

Optical characters, oxygen permeability, film impact, pinhole resistanceand vacuum deep drawing processability of thus obtained film weremeasured according to the method of evaluating film properties in (3).As a result, the resin composition film of Example 10 exhibited similaroxygen permeability to EVOH single film in Comparative Example 8 andsignificant improvements in film impact, pinhole resistance and vacuumdeep drawing processability as shown in Table 4.

Example 10

Resin composition film was prepared using the same method as in Example1, except that 6-Ny in example 1 was changed for 6, 12-Ny (EMS). Thusobtained film was evaluated according to the method of evaluating filmproperties in (3). As a result, as shown in Table 4, the resincomposition film of Example 10 exhibited similar oxygen permeability toEVOH single film in Comparative Example 8 and significant improvementsin film impact, pinhole resistance and vacuum deep drawingprocessability.

Examples 11 and 12

Three-layer cast film (55 μm thickness of a laminate film whose layersare in the ratio of 15/10/30) consisting of an outer layer of EVOH resincomposition prepared as in Example 1, and intermediate layer of maleicanhydride modified polyolefin resin (Admer NF520 manufactured by MitsuiPetrochemical Industries, Ltd.) and an inner layer of resin listed inTable 5 was formed on the molding conditions described in Table 5 usinga multilayer co-extrusion molding method.

Optical characters and oxygen permeasbility of thus obtained films weremeasured according to the method of evaluating film properties in (3).The results are shown in Table 5. As a result, it was confirmed thatEVOH resin composition according to the present invention can be formedinto multilayer film using a normal molding method, the same way asEVOH, and that the multilayer films exhibit the same good opticalcharacters and oxygen permeability as single film (Example 1).

                  TABLE 1                                                         ______________________________________                                        Ionomer Resin Materials Used in Examples and Comparative Examples             Ionomer          MAA           Neutral-                                       resin            content       ization MER                                    No.   Copolymer  (mol %)  Ion  value (%)                                                                             (g/10 min)                             ______________________________________                                        IO-1  Ethylene-  7.5      Zn   40      0.9                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-2  Ethylene-  5.3      Zn   59      0.7                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-3  Ethylene-  4.3      Zn   36      1.5                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-4  Ethylene-  3.1      Zn   30      0.8                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-5  Ethylene-  6.7      Na   36      2.1                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-6  Ethylene-  3.1      --    0      1.5                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               IO-7  Ethylene-  3.5      Na   50      1.3                                          methacrylic                                                                   acid (MAA)                                                                    copolymer                                                               ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________    Ethylene-Vinyl Alcohol Copolymer Resin (EVOH) and Polyamide Resin             Materials Used in Examples and Comparative Examples                                                  Melting                                                                             Density                                                   Monomer       point (° C.)                                                                 (g/cm.sup.2)                                                                      Commercial name                              __________________________________________________________________________    Ethylene-vinyl                                                                         Ethylene: 32 mol %                                                                          181   1.19                                                                              Kuraray Eval EP F101A                        alcohol copolymer                                                                      Vinyl alcohol: 68 mol % Manufactured by Kuraray                      (EVOH)                           Co., Ltd.                                    Nylon 6                                                                       Caprolactam                                                                            225           1.14  Amilan OM1010T                                   (6-Ny)                           Manufactured by Toray                                                         Industries, Inc.                             Nylon 6,12                                                                    Caprolactam: 80 wt %                                                                   199-203             UBE Nylon 7024B                                  copolymer (6,                                                                          aminododecanoic acid: 20 wt %                                                                         Manufactured by Ube                          12-Ny (UBE))                     Industries, Ltd.                             Nylon 6,12                                                                    Caprolactam: 90 wt %                                                                   200                 Grilon CF 9 6361                                 copolymer (6,                                                                          aminododecanoic acid: 10 wt %                                                                         Manufactured by EMS                          12-Ny (EMS))                                                                  __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Physical Properties of Film with Various Compositions                                                                   Pinhole   Modulus                                                     Oxygen  resistance                                                                              (MPa)                                                       perme-  (number                                                                            Deep longi-                    Weight ratio            Optical characters (%)                                                                  ability                                                                           Film                                                                              of bending                                                                         drawing                                                                            tudinal                   of           Preparation      trans-                                                                            cc/m.sup.2                                                                        impact                                                                            to cause                                                                           process-                                                                           trans-                    composition  method                                                                              Machine                                                                            haze                                                                             gloss                                                                            parency                                                                           hr atm)                                                                           (N/cm)                                                                            pinhole)                                                                           ability                                                                            verse                     __________________________________________________________________________    Ex. 1                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    11 91 69  0.081                                                                             20,000   good 35/35                          1 = 70/9/21                                                              Ex. 2                                                                              EVOH/6-Ny/IO-                                                                         Dry blend                                                                           1    12 87 47      18,300        37/35                          1 = 70/9/21                                                              Ex. 3                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    20 75 41      22,000        37/37                          2 = 70/9/21                                                              Ex. 4                                                                              EVOH/6-Ny/IO-                                                                         Dry blend                                                                           1    24 66 37      23,400                                  C. Ex. 10                                                                          EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    28 47 28      27,400        35/36                          3 = 70/9/21                                                              Ex. 5                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    22 62 46      20,800        42/39                          5 = 70/9/21                                                              C. Ex. 1                                                                           EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    28 22 6       8,300         37/36                          4 = 70/9/21                                                              C. Ex. 2                                                                           EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    29 44 22      10,500        37/36                          6 = 70/9/21                                                              Ex. 6                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    11 88 79  0.064                                                                             15,000   good 39/40                          1 = 80/6/14                                                              C. Ex. 3                                                                           EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    12 77 75  0.14                                                                              8,000    bad  42/42                          1 = 90/3/7                                                               C. Ex. 4                                                                           EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1    12 25 30  33  16,000   good                                1 = 30/21/49                                                             C. Ex. 5                                                                           EVOH/6-Ny/IO-                                                                         Melt blend                                                                          1, not able                                                                        -- -- --  --  --  --   --                                  1 = 60/30/10  to process                                                 C. Ex. 6                                                                           EVOH/IO-                                                                              Melt blend                                                                          1    40 8  1   0.067                                                                             1,900    good                                1 = 70/30                                                                C. Ex. 7                                                                           EVOH 6- Melt blend                                                                          1    5  91 82  --  7,100    not able                                                                           54/53                          Ny = 90/IO                                to process                     C. Ex. 8                                                                           EVOH    --    1    4  136                                                                              84  0.12                                                                              8,000    not able                                                                           49/52                                                                    to process                     Ex. 7                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          2    13 86 65  --  18,100                                                                            50   --                                  1 = 70/9/21                                                              Ex. 8                                                                              EVOH/6-Ny/IO-                                                                         Melt blend                                                                          2    18 74 44  --  18,900                                                                            50   --                                  2 = 70/9/21                                                              C. Ex. 9                                                                           EVOH    --    2    8  96 81  --  5,900                                                                             5    --                             __________________________________________________________________________     Ex: Example                                                                   C. Ex: Comparative Example                                               

                  TABLE 4                                                         ______________________________________                                                       Example 9 Example 10                                           ______________________________________                                        Weight ratio of composition                                                                    EVOH/6.12-Ny                                                                              EVOH/6.12-Ny                                                      (UBE)/      (EMS)/                                                            IO-1 = 70/9/21                                                                            IO-1 = 70/9/21                                   Preparation method                                                                             Melt blend  Melt blend                                       Machine             1           1                                             Optical character(%):haze                                                                         11          15                                            gloss               51          37                                            transparency        66          40                                            Oxygen permeability                                                                               0.03        0.03                                          (cc/m.sup.2 -nr-atm)                                                          Film impact (N/cm)                                                                             38,200      13,600                                           Pinhole resistance (number                                                                       >50         >50                                            of bending to case pinholes)                                                  Deep drawing processability                                                                    good        good                                             ______________________________________                                    

                                      TABLE 5                                     __________________________________________________________________________                                     Oxygen                                                                        perme-                                                  Resin temperature (° C.).sup.a)                                                    Optical characters (%)                                                                  ability                                      Inner      outer                                                                             intermedi-                                                                         inner    trans-                                                                            (cc/m.sup.2                                  resin      resin                                                                             ate resin                                                                          resin                                                                            haze                                                                             gloss                                                                            parency                                                                           hr atm)                                      __________________________________________________________________________    Example 11                                                                          Ionomer                                                                            248 220  243                                                                              9  35 17  0.05                                               (IO-7)                                                                  Example 12                                                                          L-L DPE.sup.b)                                                                     248 210  52 5  75 41  0.04                                         __________________________________________________________________________     .sup.a) Aperture of extruder cylinder: for outer/intermediate/inner resin     = 50/50/65 mm.0., Tdie 500 mm width, coat hanger die                          .sup.b) Linerlow density polyethylene (Ultzex 2021L manufactured by Mitsu     Petrochemical Industries, Ltd.)                                          

Examples 13 to 16 and Referential Example 1

As starting materials, the materials shown in Table 6 were used.

                  TABLE 6                                                         ______________________________________                                        Starting                    Maker and                                         material Contents           trademark                                         ______________________________________                                        EVOH     Ethylene-vinyl alcohol                                                                           Kuraray Inc.;                                              (composition: 32/68 mol %)                                                                       Eval EP P-101A                                    Ionomer  40 mol % zinc neutral salt of                                                                    Mitsui-Dupont                                              ethylene-methacrylic acid                                                                        Polychemical                                               (composition: 80/20%) random                                                                     Co., Ltd.;                                                 copolymer          Himilan                                           Nylon    Nylon 6/12 (composition:                                                                         Ube Industries                                             epsilon-caprolactum 80 wt. %/                                                                    Co., Ltd.;                                                 aminododecanoic acid 20 wt. %)                                                                   7024B                                                      copolymer                                                            Calcium  --                 Asahi Denka                                       stearate                    Co., Ltd.;                                                                    calcium                                                                       stearate CS-F                                     Anti-                       Ciba Geigy;                                       oxidant                     Irganox 1010                                      ______________________________________                                    

The ethylene-vinyl alcohol copolymer (EVOH), the ionomer ofethylene-methacrylic acid random copolymer, nylon, calcium strarate, andthe anti-oxidant as shown in Table 6 were added to a Laboplastomill (100ml in amount) in volume shown in Table 7. Under an atmosphere ofnitrogen, they were kneaded at a block temperature of 240° c. and with arotor turning at 60 rpm for 60 minutes. By examining the variations ofthe torque with time, the heat stability of the resin composition wasevaluated.

The results are described in Table 7. It is presumed that calciumstearate has an effect of suppressing the heat-crosslinking or heatdegradation of the resin composition, and that the heat stability of theresin composition is improved. In comparison with Referential Example 1in which calcium stearate was not added. Examples 13 to 16 in whichcalcium stearate were added in an amount of 0.1 to 1.0 parts by weightshow the extremely decreased values of the elevation of torque.

                  TABLE 7                                                         ______________________________________                                        Compounding                                                                   (parts by  Examples            Ref.                                           weight)    13       14     15     16   Example 1                              ______________________________________                                        EVOH       70       70     70     70   70                                     Ionomer    21       21     21     21   21                                     Nylon      9        9      9      9    9                                      Calcium                                                                       stearate   0.1      0.3    1.0    0.1  --                                     Anti-oxidant                                                                             --       --     --     0.1  --                                     Variations with time of torque (kg.m)                                         after 15 min.                                                                            2.1      1.8    1.8    2.0  2.3                                    after 30 min.                                                                            2.3      2.1    2.1    2.2  2.9                                    after 45 min.                                                                            2.7      2.5    2.4    2.5  3.8                                    after 60 min.                                                                            3.1      3.0    2.9    3.0  4.4                                    ______________________________________                                    

According to the present invention, addition of predetermined quantitiesof specific ionomer and polyamide with ethylene-vinyl alcohol copolymercan improve impact resistance, flexibility, processability, pin-holeresistance, deep-drawing property, etc., without damaging excellentgas-barrier property, transparency, etc., of said copolymer so muchComposition of the present invention can be molded, by making best useof these properties, into film, sheet, container, etc., by variousmolding methods such as extrusion molding, injection molding, blowmolding, vacuum forming and pressure forming.

What is claimed is:
 1. A thermoplastic resin composition consistingessentially of:a) 50 to 85 parts by weight ethylene vinyl alcoholcopolymer; b) 10 to 40 parts by weight of an ionomer ofethylene-carboxylic acid copolymer, said ionomer is an ionomerneutralized with a member selected from the group consisting of zinc, analkali metal, and an alkaline-earth metal, and the degree ofneutralization is 10 to 90%; and c) 1 to 25 parts by weight of apolyamide; wherein said carboxylic acid is present in said ionomer at alevel of 5 to 12 mole % of said ionomer.
 2. The thermoplastic resincomposition of claim 1, wherein said ionomer is an ionomer neutralizedwith zinc.
 3. The thermoplastic resin composition of claim 1, whereinthe ethylene vinyl alcohol copolymer contains 40 to 85 mole % vinylalcohol.
 4. The thermoplastic resin composition of claim 1, wherein thepolyamide is a polyamide or a copolyamide having a melting point of lessthan 240° C.
 5. The thermoplastic resin composition of claim 1, whereinthe thermoplastic resin composition further comprises a fatty acid metalsalt in an amount of 0.01 to 3 parts by weight per 100 parts by weightresin.
 6. A packaging film wherein said film has at least one layer of athermoplastic resin composition consisting essentially of:a) 50 to 85parts by weight ethylene vinyl alcohol copolymer; b) 10 to 40 parts byweight of an ionomer of ethylene carboxylic acid copolymer, said ionomeris an ionomer neutralized with a member selected from the groupconsisting of zinc, an alkali metal, and an alkaline-earth metal, andthe degree of neutralization is 10 to 90%; and c) 1 to 25 parts byweight of a polyamide;wherein said carboxylic acid is present in saidionomer at a level of 5 to 12 mole % of said ionomer.
 7. The packagingfilm of claim 6, further comprising at least one layer of an olefinpolymer.